Process of melting ferro-alloys and keeping them in liquid state.



W. SGHEMMANN & J. BRONN. PROGBSS 0F MELTING PERRO ALLoYs AND KEEPING THEM 1N LIQUID STATE.

APPLOATION FILED DEG.30, 1912.

1,061,0*1 6. l l Patented May 6,

wbt/weones WILHELM SCHEMMANN AND J EGOR BRONN, F ROMBACHER, HTTENWERKE, 0F ROMBACH,

MANY. n

rino

ROMBACH, GERMANY, ASSIGNQRS T0 GERMANY, A CORPORATION OF GER- PROCESS 0F MELTIN G FEiRRO-ALLOYS AND KEEPING THEM IN LIQUID STATE.

, in Liquid State,.of which the following is a specification.

The advantages of an addition of ferromanganese in liquid form to the ingot-iron or mild steel to b e deoXidized, have been pointed out heretofore by us in United States Letters Patent No. 915,488 obtained by us, and we have recommended for .this

purpose the employment of an electric furnace with pure resistance heating. It has been found,however, by continuous practical working of these furnaces that although metal could be veasily melted in the trough-- Y furnaces therein suggested,that gradually a great deal of slag was collected in the melting trough, which slag remained tough and had to be removed from time to time by.

means of tools, which caused frequent interruptions in the working of the furnaces, while the troughs were liable to be subjected to damage. Vhen, however, it is attempted to melt ferro-manganese in an electric arcfurnae such asis generally used for refining steel, a thick brown smoke begins at once to escape from the furnace owing to the com- 'bustion and evaporation of the manganese,

and the loss of manganese which takes place is so great that 'the remelting ganese becomes unprofitable.

It is well known that in electric arc-furnaces which are used in the refining o-f steel,

the .drop of the' tension within the electricarc, that is' to say, when measured between the carbon-block and the metal bath, amounts to fromv45-75 volts. It has been found, however, that when the carbon elec-- trode is lowered to such'an extent that it just touches the surface of the bath, and that when such a tension of the current is used, that the dilerence or drop of tension between the carbon and. the metal bath amounts to only from 16-18 volts, and that 'this drop is below the electromotive counterforce of the arc, which is generally taken to be about 30 volts, it is possible to obtain, by the contactresistance thus produced, an

Specification of Letters Patent.

Application filed December 3 vthe heating cannot be of ferro-man-vk Figs. 6 and -ThS Can be easily Patented May 6, 1913.

0, 1912. Serial No. 739,288.

amply sufficient heating of the melting bat-h without any noticeable loss of manganese taking place. Y, i

In view ofthe fact that in carrying out the vpresent invention, the electrode 'just touches the free surface of the metal bath,

regarded as being effected by but by means of the contact resistance between the electrode and the free surface of the bath. The Vterm contact resistance heating is thereforeused hereafter to distinguish this method of heating' from the ordinary flame arc and from ordinary resistance heating, and is infact, similar to the known method of leatingby bad surface contact or so-called semi-'arcing which method has been' used for melting ferromanganese.

rlhe invention consists in a process for melting ferro-manganese and similar alloys in which the melting is effected bynieans of contact resistance heating, the voltage drop between each of the movableblock electrodes and the bath of molten material being less than thirty volts.'

The accompanying drawings illustrate by way of example some constructionsof a furnace for carrying out this invention'.

Figures l and 2, are vertical cross sections at right angles to each other of a furnace for three phase'current, Figs and 4 are respectively, a sectional plan and a sectional elevation of a modified construction of furnace. Fig. 5 is-a 'sectional plan of a modification of the vpreceding construction.

tion. y

The furnace shown in Figs. 1 and 2 is elevation and a. plan of a further modifica- 7 are respectively a sectional,

means of an ordinary ilame arc,

designed for three-phase current; it is similar in its construction to the usual steel furnaces and like these it can also be operated with ordinary alternating current, that is to' say with only two electrodes. It is however indispensable that, as already stated, the voltage drop between each electrode and the belt shall not exceed the limits above stated.

the source of current to which the electrodes are to be connected of suitable low voltage; In most cases the shall supply a current' effected by arranging that 1 current can be supplied by-stationai-y4 trans# formers. When for instance, a single phase electricfurnace having Vonly one contact resistance between the movable electrode and the metal bath (Figs. 6 and 7) is required tcfwork in the manner herein described with 'a voltage drop of about 2O volts, then the voltage between the secondaryterminals of c the transformer must not exceed 20 volts y'(including any loss of voltage). In single 10 phasey furnaces having two movable elec 'trodes, the voltage drop between each electrode and the metal bath must amount to volts. This discovery that by a kind of .heating by contact resistance it is possible 5to obtain a supply of heat which is quite sufficient for melting' and keeping in the molten'state ferro-manganese and the resulting slag, may be fa plied directly to a furnace of the type ,il ustrated in Figs. 3 and 4. The metal bath is inserted as a heat-l ing resistance in a channel, and the slag which forms on the surface of the bath and which is not suiciently heated by the re- 4sistance heating, is, however, kept hot' by the heat developed owing to the contact resistance' between the free surface of the metal bath and the electrodes. ',lhe slag above Ireferred to is formed owing to the.

fact that, during' the heating a layer of oxide forms on the surface of the metal which oxids attack the material of the fur- 'hace and thus form slag. It is to be understood that' only a very thin layer of slagfis formed which is'blown'back or forced away around the electrode bythel action of the electric current.v In wor 'ng'this combined furnaceI with three-'phase current. as shown in Figs. 3 and 4, has the following advantages over the furnace shown inFigs. 1 and 2 namelyz, 1. The consumption of the expensive -movable "block electrodes .is reduced to, one third,` and the labor of changing and adjusting the electrodes is diminished.` 2. The lactual bath and the covering y `laver of slag can be, heated independently Hof each other -at will with much greater convenience'because the metal bath is heating chiefly vin the channels by pure resistance! heatingwhereas the slag covering on lthe 5o bath vis heated by means of the contact resistance` as. describedl above.' This regula-- tion of the heating is effected most simply by keeping the level ofgthebath inthe channels higher. or lower whereby the conductive"` cross sectional area vof 'the metal bath, ,and consequently also the 'current passing through the same is varied, The cross sec-g tionof the channelsl' and 2 isV preferably made such that the internal resistance of the metal bath in them is'approximately';

lequalto the resistance .between the metal bath and the electrode 9. As shown in Figs. 3 and'4 the two 'channels'l and 2 open into "a wide hearth 3 which is heated by means B5 of the electrode 9;'7B1'ocks 4 of carbon or graphite are arranged at the two closed ends of the channels. unlike ingot iron ferrofmanganese is not capable of dissolving carbon. Consequently the electrode blocks 4, which are let into the ends ofthe channels are practically not subjected to any wear and tear except where they come in contact with the external atlVe have discovered that mosphere, that is to say, at their upper parts where they are raised to incandescence by the heat of the current and the heat of conduction, so that a'slow combustion takes place. With the object of reducing this l `wear and tear as far, as possible and of avoiding the inconvenient unmaking and remaking of the contacts or connections for the heavy current supply the current connectlons are. arranged as follows z-Flexible cables lead from the terminals of the transformers to the copper .bars 5. These copper bars are clamped around a water cooled metal body 6 mounted on carbon slabs resting on the carbon blockl 4. For the purpose v.ot maintaining a very intimate contact be .tween the-metal body and the block 4,\the

metal body 6 is pressed against the block by means of a steel screw 7 and an intermediate insulating piece 8. The two channels 1 and 2,`.and the carbon or graphite block 9 which depends into the hearth', are connected respectively to' the current phases a b c of the three phase current. Fig. 5 is a cross seccharged mainly in largelumps into the fur# nace these lumps melt but slowl and thus interfere with the continuous-wor ing which ought to keep step with the working *ofthev steel making plant. ForI this reason it may be preferable under certain circumstances to employinstead of the furnace' shown in Figs. 3 and 4, aseries of furnaces as' shown in Figs.' 6 and 7 for working inconnection `tionof a similar furnace which is however,

with steel-making plant'. Each of the three furnacescan be connected accordingto the ,available voltage,-'either to two phases of the'three-phase current, for instance fur- :naceI to the phasese and b, furnace VII to the'phases b and/0, furnace'III tothe phases a and c, or if the voltagefistoo high "it may be connected tothe two terminals be-` longing to the same phase.` These threelfurnaces work simultaneously,vekcept'that they are I charged and i discharged;` intermittently.

'i125 charges per hour are madey even in the largest `ysteel works, each furnacethas therefore three uarters of an hour for heating andmelting Since` never more than foury `vcornverter t e fresh charge of ferro manganese.

The furnaces hereinbefore described are` and in what manner the 'same is to beperformed, we declare that what we claim is:-

1. The' process herein described of melt ing ferro-manganese and similar alloys which consists in. vmelting` the ,alloys by means of contact resistance heating using a voltage drop between each ofthe movable block electrodes and the bath'of molt-,en material which is less than thirty volts. i

2. The process herein describedk of melting Aferro-man'ganese and similar alloys which consists in melting. the alloys by means of Contact resistance'heati'ng in oonjunction WithA ordinary resistance .heating lusing a voltage drop between each ofthe 20 movable block electrodes and the bathi of molten, materiall which is less than thlrty volts.

3. The-process herein describedv of melting ferro-manganese and similar'alloys Which consists in so disposing the movable elec- `tro'de that the'clro'p or diference of tension between the electrodes and the bath'is less than 30.` Volts.

In testimony, that We claim-the foregoing 3n is our lnvention, .We have signed ournarnes in presence of two subscribing Witnesses.

'WILHELM SCHEMMANN.

JEGOR BRONN. Witnesses: LoUIs VANDORY,

BEssIE F, DUNLAP. 

